Stomorgyl Dosage and administration By oral administration. For dogs and cats, 23.4 mg spiramycin and 12.5 mg metronidazole/kg bodyweight, once daily for 5 to 10 days. STOMORGYL 2 1 tablet/2 kg bodyweight once daily for 5–10 days. STOMORGYL 2 is the most suitable for use in cats. STOMORGYL 10 1 tablet/10 kg bodyweight once daily for 5–10 days. STOMORGYL 20 1 tablet/20 kg bodyweight once daily for 5–10 days.